Optical communications system

Abstract

An optical communications system is disclosed. In the optical communications system, a received light source is modulated in accordance with an electrical signal using an acousto-optic modulator. The acousto-optic modulator modulates an amplitude of the received light source in accordance with an amplitude of the electrical signal. Furthermore, an angle of diffraction of a beam produced by the acousto-optic modulator is a function of a frequency of the electrical signal. The optical communications system is equipped with a waveplate that converts a polarization of the diffracted beam to correspond to the polarization of an undiffracted beam. Improved detection and recovery of the electrical signal may be achieved due to the polarization correspondence between the diffracted beam and the undiffracted beam.

What is claimed is: 
     
       1. An optical communication system comprising:
 an acousto-optic modulator configured to receive an electrical signal and modulate a light beam in accordance with the received electrical signal to produce an undiffracted beam and at least one diffracted beam, the undiffracted beam having a first polarization and the at least one diffracted beam having a second polarization, the first polarization and the second polarization being different; and 
 a waveplate configured to receive the at least one diffracted beam as an input, convert the second polarization of the at least one diffracted beam to correspond to the first polarization and provide the at least one diffracted beam having the converted polarization. 
 
     
     
       2. The system of  claim 1  wherein the acousto-optic modulator is further configured to receive the light beam from a laser source. 
     
     
       3. The system of  claim 1 , further comprising:
 at least one lens configured to receive the undiffracted beam and the at least one diffracted beam having the converted polarization and align the undiffracted beam and the at least one diffracted beam having the converted polarization for transmission to an optical receiver. 
 
     
     
       4. The system of  claim 3  wherein the optical receiver is a photodetector. 
     
     
       5. The system of  claim 1  wherein the first polarization of the undiffracted beam is linear, circular or orthogonal linear. 
     
     
       6. The system of  claim 1  wherein the waveplate is further configured to convert the second polarization of the at least one diffracted beam from linear, circular or orthogonal linear to correspond to the first polarization of the undiffracted beam. 
     
     
       7. The system of  claim 1  wherein an amplitude of the at least one diffracted beam is modulated in accordance with an amplitude of the received electrical signal. 
     
     
       8. The system of  claim 1  wherein the acousto-optic modulator is a Bragg cell. 
     
     
       9. The system of  claim 1  wherein the first polarization of the undiffracted beam is the same as a polarization of the light beam. 
     
     
       10. The system of  claim 9  wherein modulating the light beam, by the acousto-optic modulator, in accordance with the received electrical signal causes the second polarization of the at least one diffracted beam to be different than the polarization of the light beam. 
     
     
       11. The system of  claim 1  wherein an angle of diffraction of the diffracted beam is a function of a frequency of the received electrical signal. 
     
     
       12. An optical transmitter comprising:
 a laser source configured to provide a laser beam; 
 a Bragg cell configured to modulate the laser beam in accordance with an electrical signal to produce an undiffracted beam and a diffracted beam, the undiffracted beam having a first polarization and the modulation causing the diffracted beam to have a second polarization that is different from the first polarization of the undiffracted beam; and 
 a waveplate configured to receive the diffracted beam from the Bragg cell and convert the second polarization of the diffracted beam to correspond to the first polarization of the undiffracted beam, the waveplate being further configured to output diffracted beam having the converted polarization. 
 
     
     
       13. The optical transmitter of  claim 12  wherein:
 the first polarization of the undiffracted beam is linear, circular or elliptical; and 
 a polarization of the output diffracted beam matches the linear, circular or elliptical polarization of the undiffracted beam. 
 
     
     
       14. The optical transmitter of  claim 12  wherein an amplitude of the diffracted beam is modulated to be a function of an amplitude of the electrical signal. 
     
     
       15. The optical transmitter of  claim 12  wherein an angle of diffraction of the diffracted beam is a function of a frequency of the electrical signal. 
     
     
       16. The optical transmitter of  claim 12 , further comprising:
 at least one lens configured to receive, from the Bragg cell, the undiffracted beam and the diffracted beam and align the undiffracted beam and the diffracted beam for transmission to an optical receiver. 
 
     
     
       17. The optical transmitter of  claim 16  wherein the optical receiver is a photodetector. 
     
     
       18. An optical communication system comprising:
 an acousto-optic modulator configured to receive a waveform and modulate the waveform in accordance with an electrical signal to produce an undiffracted beam and a diffracted beam, at least one of the undiffracted beam or the diffracted beam having a first polarization and at least one other of the undiffracted beam or the diffracted beam having a second polarization, the first polarization and the second polarization being different due to the modulation of the waveform; 
 a waveplate configured to convert the second polarization to correspond to the first polarization. 
 
     
     
       19. The optical communication system of  claim 18  wherein the waveplate is further configured to output the at least one other of the undiffracted beam or the diffracted beam having a polarization corresponding to the first polarization for transmission. 
     
     
       20. The optical communication system of  claim 19 , further comprising:
 composite beam launching optics configured to receive the at least one other of the undiffracted beam or the diffracted beam from the waveplate and transmit the at least one other of the undiffracted beam or the diffracted beam to an optical receiver.